System and method for reducing motion blur using CCD charge shifting

ABSTRACT

A method and system is disclosed for reducing motion blur using CCD charge shifting. In one embodiment, photodiode wells are exposed for a set of successive exposures with each exposure duration being a fraction of a total exposure time. After each successive exposure, the photodiode wells integrate signal charges and shift them to corresponding storage lines. The shifted signal charges are then shifted along the storage lines for a specified number of storage units. At the same time, the CCD is moved in the direction of a leading edge of the CCD. The photodiode wells are then exposed for another exposure to produce another set of signal charges, which are shifted to the storage lines. Signal charges from the successive exposures are accumulated at the storage lines. After all successive exposures have been taken, the accumulated signal charges are shifted to a serial shift register and output to form an image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/344,341, filed Dec. 26, 2008, which claims the benefit of U.S.Provisional Patent Application No. 61/006,128, filed on Dec. 26, 2007,entitled “System and Method for Reducing Motion Blur Using CCD ChargeShifting” by lain Richard Tyrone McClatchie, which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to digital imaging using charge-coupleddevices (CCDs), and in particular to reducing motion blur caused by CCDmovement.

BACKGROUND OF THE INVENTION

When taking an image with a camera moving during a period of exposure,an object in the image that is not moving at the same rate as the cameramay appear blurred or smeared along the direction of relative motion.This effect is often called motion blur. The longer the exposure time,more the imaged object moves with respect to the camera and the more thepicture is blurred. One simple solution to avoid motion blur is fixingthe camera position with respect to the objects to be captured in theimage. There are also techniques such as image stabilization, vibrationreduction, and anti-shake techniques to counteract the motion of acamera to reduce motion blur. However, such techniques only apply whenthe motion blur is caused by a slight motion of the camera, such asshaking, vibrating, etc. These techniques can not help in situationswhere the camera motion is significant.

Because motion blur is related to the image exposure time, reducing theexposure time can reduce the amount of motion blur. However, a shorterexposure time also results in a lower amount of light entering thecamera sensor, which in turn, affects the quality of the picture. Thatis, a picture produced with a shorter exposure time appears to be darkerthan a picture produced with a longer exposure time.

With the introduction of digital cameras and advances of digitalimaging, there are also efforts to reduce motion blur usingsoftware-based image processing techniques to process digitalizedpictures (or digital images) after they are produced. However, becausedigital images alone do not provide information about the cameramovement during exposures, results from software-based techniques areoften not as good as solutions applied on the camera itself.

BRIEF SUMMARY OF THE INVENTION

A method and system is disclosed for reducing motion blur usingcharge-coupled device (CCD) charge shifting. In one embodiment,photodiode wells and storage lines on a CCD are reset for an exposure.The photodiode wells are then exposed for a first exposure duration as afraction of a total exposure time. The photodiode wells integrate signalcharges during the exposure and shift the signal charges tocorresponding storage lines. The signal charges are shifted along thestorage lines for a specified number of storage units. At the same time,the CCD is moved in the direction of a leading edge of the CCD for thesame specified number of storage units. Then the photodiode wells areexposed for a second exposure duration as a fraction of a total exposuretime. The photodiode wells integrate a second set of signal charges andshift the second set of signal charges to the corresponding storagelines. The shifted second set of signal charges are accumulated with theexisting signal charges at the storage lines. An additional number ofsuccessive exposures can be produced following the above procedure ifnecessary. Then the accumulated signal charges from all the successiveexposures are shifted to a serial shift register and output from theserial shift register to form an image.

Further embodiments, features, and advantages of the invention, as wellas the structure and operation of the various embodiments of theinvention are described in detail below with reference to accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

Embodiments of the invention are described with reference to theaccompanying drawings. In the drawings, like reference numbers mayindicate identical or functionally similar elements. The drawings inwhich an element first appears is generally indicated by the left-mostdigit in the corresponding reference number.

FIG. 1 is an illustrative diagram of the structure of a charge-coupleddevice (CCD) according to one embodiment of the invention.

FIG. 2 is an illustrative diagram of the structure of a system forreducing motion blur using CCD charge shifting according to oneembodiment of the invention.

FIG. 3 is an illustrative diagram of the procedure of shifting signalcharges from photodiode wells to storage lines in the CCD according toone embodiment of the invention.

FIG. 4 is an illustrative diagram of the procedure of shifting thesignal charges along the storage lines in the CCD according to oneembodiment of the invention.

FIG. 5 is an illustrative diagram of the procedure of shifting thesignal charges of a successive exposure from the photodiode wells to thestorage lines in the CCD according to one embodiment of the invention.

FIG. 6 is an illustrative diagram of the procedure of shifting theaccumulated signal charges from the storage lines to a serial shiftregister of the CCD according to one embodiment of the invention.

FIG. 7 is a flowchart of an exemplary routine for reducing motion blurusing CCD shifting according to one embodiment of the invention.

FIG. 8 is a flowchart of an exemplary routine for integrating andshifting signal charges in the CCD to reduce motion blur according toone embodiment of the invention.

FIG. 9 is an illustrative diagram of a color scheme of a Bayer mosaicCCD.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to reducing motion blur in digital imagingcaused by movements of a charge-coupled device (CCD). In the detaileddescription of the invention herein, references to “one embodiment”, “anembodiment”, “an example embodiment”, etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described.

A CCD-based digital camera uses a CCD image sensor to sense the lightintensities to which it is exposed in order to produce digital images.FIG. 1 shows an illustrative diagram of several key components of a CCD100 according to one embodiment of the invention. CCD 100 includes acollection of photodiode wells 110, a set of storage lines 120, storagecontrol lines 130, shifting control lines 140, and an array of serialshift registers 150. Photodiode wells correspond to pixels in an imageproduced by a digital camera using CCD 100 as an image sensor. In oneembodiment, each photodiode well 110 corresponds to one pixel in animage. In one embodiment, photodiode wells 110 are exposed to light fora duration of time (or exposure time). During the exposure, eachphotodiode well 110 collects (or integrates) a signal chargeproportional to a light intensity at its location. The set of storagelines 120 store signal charges integrated at photodiode wells. Eachstorage line 120 includes a set of storage units. Each storage unitcorresponds to a neighboring photodiode well 110. After the signalcharges are integrated at photodiode wells 110, storage control lines130 control the shifting of the integrated signal charges from each ofthe photodiode wells to corresponding neighboring storage unit instorage lines 120. Therefore, each storage unit in the storage lines canstore signal charges corresponding to a pixel. Then, shifting controllines 140 control the shifting of the signal charges from storage lines120 to serial shift register 150. The shifted signal charges at serialshift register 150 can be output to produce a digital image.

In one embodiment of the invention, because of the charge-shiftingfeature of a CCD, motion blur caused by movement of a CCD-based digitalcamera can be reduced by integrating and shifting signal charges fromsuccessive exposures. For example, a total exposure time required toproduce an image can be divided into a set of successive exposuredurations. In this manner, a set of successive exposures are producedwithin the total exposure time instead of having just one exposureduring the total exposure time. Each of the successive exposures has acorresponding exposure duration in the set of successive exposuredurations. For example, if a total exposure time is T seconds and twosuccessive exposures are desired, each successive exposure duration inthe set of successive exposure durations may be one-half of T seconds.

Signal charges for each successive exposure may be integrated andshifted while moving the CCD along a direction of the CCD at a specifiedspeed. In one embodiment, the direction of the CCD is the direction of aleading edge of the CCD. A leading edge of the CCD, such as leading edge160 in FIG. 1, is the edge of the CCD oriented towards the direction ofmotion of the CCD. In other embodiments, the CCD may be moved along adirection depending upon particular applications. The signal chargesfrom successive exposures are accumulated in the storage lines andshifted to the serial shift register for output. The successive exposuredurations may be set to match the rate at which the CCD moves. Byshifting the signal charges along the storage lines in a directioncorresponding to the CCD moving direction, the signal charges from eachsuccessive exposure may correspond to the same scene being captured bythe CCD. Because each successive exposure duration is shorter than thetotal exposure time, the corresponding successive exposure will producesignal charges with less motion blur. The accumulation of the successivesignal charges acts to enhance the light intensity for each pixel andimprove the quality of the produced final image.

FIG. 2 shows an illustrative structure of the system for reducing motionblur using CCD charge shifting according to one embodiment of theinvention. System 200 includes a CCD 100 as an image sensor, a shutterunit 210 that controls the system to be exposed to light, ashutter-control unit 220 that controls the operation of the shutterunit, a delay-and-integration-control unit 230 that controls the delay,integration, and shifting of signal charges of the CCD, asignal-charge-output unit 240 that controls the signal charges to beoutput to produce an image, and a movement unit 250 that controls themovement of the CCD.

Delay-and-integration-control unit 230 includes a charge-reset module231, an integration-and-shifting module 232, a storage-shifting-controlmodule 233, a delay-shifting-control module 234, an accumulating-controlmodule 235, and a serial-shifting-control module 236. Charge-resetmodule 231 controls resetting photodiode wells 110 and storage lines 120for an exposure. Integration-and-shifting module 232 controlsintegrating signal charges at photodiode wells 110 during an exposureand shifting the integrated signal charges to storage lines 120.Storage-shifting-control module 233 controls shifting signal chargesalong storage lines 120. Delay-shifting-control module 234 controlsdelaying the shifting of signal charges from storage lines 120 to serialshift register 150 for a pre-defined duration. Accumulating-controlmodule 235 controls accumulating the signal charges shifted fromphotodiode wells 110 with existing signal charges at storage lines 120.Serial-shifting-control module 236 controls shifting signal charges fromstorage lines 120 to serial shift register 150.

In a CCD-based camera mounted on a moving vehicle and used to takestreet view pictures, motion blur may occur because of the cameramovement. In general, when taking a picture, a shorter exposure time mayreduce the motion blur caused by the camera movement. However, this alsocauses the photodiode wells of the CCD to receive a lower amount oflight compared with a longer exposure. This produces low quality images(e.g., dark images). According to one embodiment of the invention,accumulating signal charges from successive, short-duration exposuresenhances the signal charges for most pixels in the produced image andimproves the image quality.

FIG. 7 is a flowchart of an exemplary routine 700 for reducing motionblur by CCD charge shifting when producing an image according to oneembodiment of the invention. Although routine 700 will be described withreference to CCD 100 and system 200, one of skill in the art willrecognize that routine 700 may be used with any type of CCD or controlsystem without departing from the spirit and scope of the presentinvention.

In step 710, signal charges from a plurality of successive exposures areintegrated and shifted on a CCD. In one embodiment of the invention, atotal exposure time for producing an image is divided into a set ofdurations for successive exposures. That is, signal charges from a firstexposure are integrated and shifted from photodiode wells, such asphotodiode wells 110, to storage lines, such as storage lines 120.Before storage lines 120 are reset, photodiode wells 110 are exposedwith a second exposure. Signal charges from the second exposure are thenintegrated and shifted from photodiode wells 110 to storage lines 120.

In step 720, the signal charges from successive exposures areaccumulated in the storage lines. For example, the signal charges may becombined or further integrated in storage lines 120.

In step 730, the accumulated signal charges are shifted from the storagelines, such as storage lines 120, to the serial shift register, such asserial shift register 150.

In step 740, the signal charges in the serial shift register, such asserial shift register 150, are output to form an image.

FIG. 8 is a flowchart of an exemplary routine 800 illustrating moredetails about exemplary routine 700. FIG. 8 will be further describedwith reference to FIGS. 1 and 3-6. FIGS. 3-6 show illustrative diagramsof the integration, accumulation, and shifting of signal charges insidethe CCD according to one embodiment of the invention. One of skill inthe art will recognize that the routine of FIG. 8 may apply to otherCCDs and systems without departing from the spirit and scope of thepresent invention.

In step 810, photodiode wells 110 and storage lines 120 of CCD 100 arereset to clear any existing signal charges.

In step 820, photodiode wells 110 are exposed to light. The amount oflight received by photodiode wells 110 is controlled by shutter unit210. Shutter unit 210 is in turn controlled by shutter-control unit 220.Exposure time (or duration of an exposure) may be controlled by shutterunit 210 or shutter-control unit 220 also control the exposure time.

In step 830, photodiode wells 110 integrate a set of signal charges dueto the exposure. The integrated signal charges are then shifted tostorage lines 120. For example, as illustrated in FIG. 3, afterphotodiode wells 110 collect and integrate signal charges 310 for anexposure, integration-and-shifting module 232 toggles storage controllines 130. This triggers the process of shifting 320 of integratedsignal charges 310 from photodiode wells 110 to corresponding storagelines 120.

In step 840, when signal charges 310 are shifted to storage lines 120,signal charges 310 accumulate with existing signal charges in storagelines 120. If signals charges 310 correspond to a first exposure, thereare no existing signal charges in storage lines 120 and the accumulationonly includes the shifted signal charges from photodiode wells 110.

After the signal charges have been accumulated in the storage lines,routine 800 proceeds to step 850. In step 850, system 200 tests whetheranother exposure is needed. In one embodiment, system 200 can set atotal number of successive exposures to produce an image. System 200 maycompare the number of produced successive exposures for the image to beproduced with the total number of successive exposures. If the number ofproduced successive exposures is smaller than the total number, anotherexposure is needed. Routine 800 proceeds to step 852.

In step 852, the accumulated signal charges are shifted along storagelines 120 for a specified number of storage units. As mentioned above,each storage unit may correspond to a pixel in the produced image. Forexample, as illustrated in FIG. 4, storage-shifting-control module 233toggles shift control lines 140. This triggers the shifting 420 ofsignal charges 310 along storage lines 120 for a specified number ofstorage units.

The specified number of storage units for the shifting of signal chargesalong storage lines 120 is determined by several factors, including thetype of the CCD (e.g. Bayer mosaic CCD or panchromatic CCD, etc.), thespeed of the CCD movement, the number of successive exposures, and imagequality desired by a user, etc. Different types of CCDs include, forexample and without limitation, Bayer mosaic CCDs, RGBE CCDs, andpanchromatic CCDs.

One type of CCD used in many digital cameras is a Bayer mosaic CCD. ABayer mosaic CCD uses a Bayer filter over the CCD that allows thephotodiode wells to integrate signal charges for individual RGB colors(i.e. red, green, and blue). FIG. 9 shows an illustrative diagram of theRGB color distribution of a Bayer mosaic CCD. In FIG. 9, R representsred, G represents green, and B represents blue. The RGB colorarrangement over the CCD may produce as many as green pixels as red andblue combined to mimic the human eye's greater resolving power withgreen light.

In a Bayer mosaic CCD, every other photodiode well in an orthogonaldirection of the CCD has a same color arrangement. Therefore, if a Bayermosaic CCD is used in one embodiment, the specified number of storageunits for the shifting of the signal charges along the storage lines andthe CCD movement will be a multiple of two.

A RGBE CCD is similar to a Bayer mosaic CCD with a different colorfilter (i.e. RGBE filter) over the CCD. The RGBE filter has a colordistribution of red, green, blue and emerald (similar to the colorcyan).

Another type of CCD is a panchromatic CCD. A panchromatic CCD usesphotodiode wells that are all sensitive to the same wavelength(s) oflight and collect a larger amount of light when exposed. Because eachphotodiode well captures the same wavelength(s), a panchromatic CCD doesnot need a color arrangement such as the RGB color distribution in theBayer mosaic CCD. Thus, if a panchromatic CCD is used in system 800, thespecified number of storage units for the shifting of the signal chargesalong the storage lines and the CCD movement can be any natural numberdepending on image quality requirements.

Returning to routine 800 in FIG. 8, in step 854 CCD 100 is moved in adirection toward leading edge 160 of CCD 100 for the same number ofstorage units as were shifted during step 852. This ensures that signalcharges to be received by the storage units are accumulated withprevious signal charges from the same image. At the same time,delay-shifting-control module 234 delays the shifting of signal chargesfrom storage lines 120 to serial shift register 150.

After CCD 100 is moved in step 852, routine 800 returns to step 820,where photodiode wells 110 are exposed for a successive exposure tointegrate corresponding signal charges.

When routine 800 returns to step 840, signal charges already exist instorage lines 120 as a result of the first pass through steps 820through 854. For example, as illustrated in FIG. 5, after theintegration of the signal charges 510 from the successive exposure,storage control lines 130 are toggled again by integration-and-shiftingmodule 232. This triggers the shifting 520 of integrated signal charges510 of the successive exposure from photodiode wells 110 tocorresponding storage lines 120. Because signal charges 310 are stillpresent in storage lines 120, accumulating-control module 235 controlsstorage lines 120 to combine signal charges 510 shifted from photodiodewells 110 after the successive exposure with signal charges 310 instorage lines 120.

FIG. 5 also illustrates the CCD movement between exposures. In thisexemplary embodiment, signal charges 310 from the previous exposure areshifted along storage lines 120 for two storage units. At the same time,CCD 100 is moved in the direction of leading edge 160 for two storageunits. Because the signal charges from the previous exposure are shiftedalong the storage lines for, in this example, two storage units, the toptwo rows of storage units in the storage lines do not have signalcharges when the signal charges of the current exposure are shifted fromphotodiode wells 110 to storage lines 120 during shifting 520. Inaddition, because CCD 100 is moved in the direction of leading edge 160,which is the opposite direction from the direction of shifting 520occurring along storage lines 120 in this exemplary embodiment, thesignal charges integrated in photodiode wells 110 for the successiveexposure correspond to the same storage units of the signal chargesremaining in storage lines 120 from the previous exposure.

In step 850 of routine 800, if it is determined that no furtherexposures are needed, routine 800 proceeds to step 860. In step 860,accumulated signal charges are shifted to a serial shift register. Forexample, as illustrated in FIG. 6, serial-shifting-control module 236toggles shift control lines 140. This triggers the shifting 620 of theshifted signal charges 510 and accumulated signal charges 630 to serialshift register 150.

In step 860 of routine 800, accumulated signal charges in the serialshift register are output to form an image. For example, accumulatedsignal charges 610 in serial shift register 150 are output bysignal-charge-output unit 240 to form an image.

In this manner, multiple short-exposure-time signals are combined tocreate a single image with reduced motion blur.

The systems and methods of the present invention can be applied to anyCCD-based camera, including a Bayer mosaic CCD camera a panchromatic CCDcamera, etc. The present invention is not limited to reducing motionblur caused by camera movement. By moving the CCD in the direction ofmovement of an object for a number of storage units related to the speedof the object, motion blur caused by the movement of the object can alsobe reduced.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the present invention ascontemplated by the inventor, and thus, are not intended to limit thepresent invention and the appended claims in any way.

The present invention has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent invention. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A method of reducing motion blur in a digitalimage produced by a moving charge-coupled device (CCD), comprising:integrating signal charges at photodiode wells from successive exposureson the CCD, each photodiode well corresponding to a pixel of the digitalimage, by exposing the CCD to a subject, wherein the duration of eachsuccessive exposure is chosen to be a fraction of a total exposureduration that is proportional to a speed at which the CCD physicallymoves; shifting the signal charges for each successive exposure in adirection opposite to a direction of CCD motion as the CCD physicallymoves, wherein a distance of the shift is proportional to a speed atwhich the CCD physically moves; accumulating the signal charges from thesuccessive exposures in storage lines of the CCD to enhance the lightintensity of each pixel, wherein the integrating and shifting cause thesignal charges to be accumulated with other signal charges thatcorrespond to a same portion of the subject; shifting the accumulatedsignal charges from the storage lines to a serial shift register; andoutputting the accumulated signal charges from the serial shift registerto produce a digital image.
 2. The method of claim 1, wherein the CCD isa Bayer mosaic CCD, and shifting the signal charges comprises shiftingthe signal charges by two storage units along the storage lines.
 3. Themethod of claim 1, wherein the CCD is a panchromatic CCD, and shiftingthe signal charges comprises shifting the signal charges by one storageunit along the storage lines.
 4. The method of claim 1, wherein adistance of the shift is proportional to a speed at which the CCDphysically moves and is determined based on at least one of: a type ofthe CCD, a number of successive exposures, and an image quality desiredby a user.
 5. The method of claim 1, wherein the CCD is an RGBE CCD. 6.The method of claim 1, wherein accumulating the signal charges comprisesholding shifting control lines of the CCD for a specified time.
 7. Themethod of claim 1, wherein shifting the accumulated signal charges fromthe storage lines to a serial shift register comprises toggling shiftingcontrol lines of the CCD.
 8. A system for reducing motion blur in adigital image produced by a moving charge-coupled device (CCD),comprising: a CCD comprising photodiode wells, storage lines, storagecontrol lines, shifting control lines, and a serial shift register; ashutter-control unit configured to expose the CCD to a subject, whereinthe duration of each successive exposure is chosen to be a fraction of atotal exposure duration that is proportional to a speed at which the CCDphysically moves; a delay-and-integration control unit configured to:integrate signal charges at the photodiode wells from the successiveexposures on the CCD, each photodiode well corresponding to a pixel ofthe digital image; shift the signal charges for each successive exposurein a direction opposite to a direction of CCD motion as the CCDphysically moves, wherein a distance of the shift is proportional to aspeed at which the CCD physically moves; accumulate the signal chargesfrom the successive exposures in the storage lines of the CCD to enhancethe light intensity of each pixel, wherein the integrating and shiftingcause the signal charges to be accumulated with other signal chargesthat correspond to a same portion of the subject; and shift theaccumulated signal charges from the storage lines to the serial shiftregister; and a signal-charge-output unit configured to output theaccumulated signal charges from the serial shift register to produce adigital image.
 9. The system of claim 8, wherein the CCD is a Bayermosaic CCD, and the delay-and-integration-control unit is configured toshift the signal charges by two storage units along the storage lines.10. The system of claim 8, wherein the CCD is a panchromatic CCD, andthe delay-and-integration-control unit is configured to shift the signalcharges by one storage unit along the storage lines.
 11. The system ofclaim 8, wherein a distance of the shift is proportional to a speed atwhich the CCD physically moves and is determined based on at least oneof: a type of the CCD, a number of successive exposures, and an imagequality desired by a user.
 12. The system of claim 8, wherein the CCD isan RGBE CCD.
 13. The system of claim 8, wherein thedelay-and-integration-control unit is configured to accumulate thesignal charges by holding shifting control lines of the CCD for aspecified time.
 14. The system of claim 8, wherein thedelay-and-integration-control unit is configured to shift theaccumulated signal charges from the storage lines to a serial shiftregister by toggling shifting control lines of the CCD.
 15. Anon-transitory computer readable storage medium having instructionsstored thereon that, when executed by a processor, cause the processorto perform a method for reducing motion blur in a digital image producedby a moving charge-coupled device (CCD), the method comprising:integrating signal charges at photodiode wells from successive exposureson the CCD, each photodiode well corresponding to a pixel of the digitalimage, by exposing the CCD to a subject, wherein the duration of eachsuccessive exposure is chosen to be a fraction of a total exposureduration that is proportional to a speed at which the CCD physicallymoves; shifting the signal charges for each successive exposure in adirection opposite to a direction of CCD motion as the CCD physicallymoves, wherein a distance of the shift is proportional to a speed atwhich the CCD physically moves; accumulating the signal charges from thesuccessive exposures in storage lines of the CCD to enhance the lightintensity of each pixel, wherein the integrating and shifting cause thesignal charges to be accumulated with other signal charges thatcorrespond to a same portion of the subject; shifting the accumulatedsignal charges from the storage lines to a serial shift register; andoutputting the accumulated signal charges from the serial shift registerto produce a digital image.
 16. The non-transitory computer readablestorage medium of claim 15, wherein the CCD is a Bayer mosaic CCD, andshifting the signal charges comprises shifting the signal charges by twostorage units along the storage lines.
 17. The non-transitory computerreadable storage medium of claim 15, wherein the CCD is a panchromaticCCD, and shifting the signal charges comprises shifting the signalcharges by one storage unit along the storage lines.
 18. Thenon-transitory computer readable storage medium of claim 15, wherein adistance of the shift is proportional to a speed at which the CCDphysically moves and is determined based on at least one of: a type ofthe CCD, a number of successive exposures, and an image quality desiredby a user.
 19. The non-transitory computer readable storage medium ofclaim 15, wherein accumulating the signal charges comprises holdingshifting control lines of the CCD for a specified time.
 20. Thenon-transitory computer readable storage medium of claim 15, whereinshifting the accumulated signal charges from the storage lines to aserial shift register comprises toggling shifting control lines of theCCD.